Surfaced mixed epoxy method for abandoning well

ABSTRACT

A two part epoxy resin system is surface mixed in a method of plugging an abandoned well. This surface mixed epoxy resin is then placed in the well at the desired plugging depth. Finally, the mixture in situ forms a cementing plug.

This application is a continuation of U.S. patent application Ser. No.11/162,451, filed Sep. 9, 2005, herein incorporated by reference, whichapplication claims priority/benefit of U.S. Provisional PatentApplication Ser. Nos. 60/608,255, 60/608,256, and 60/608,257, all filedSep. 9, 2004, and all herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to wells, abandoned wells, welloperations, to methods, apparatus and products for operating wells. Inanother aspect, the present invention relates to wells, abandoned wells,abandoning wells, to methods, apparatus and products for abandoningwells. In even another aspect, the present invention relates wells,plugged wells, plugging wells, and to methods, apparatus and productsfor plugging abandoned wells. In still another aspect, the presentinvention relates wells, treated wells, treating wells, and to methods,apparatus and products for treating abandoned wells.

2. Brief Description of the Related Art

Wells of various types after their useful lives are shut down andusually permanently plugged for a variety of reasons. For example, wellsemployed in the production of oil and gas are usually abandoned becausethey reach the end of their useful life or they become damaged beyondrepair.

Various jurisdictions in the oil producing regions of certain countriesrequire that abandoned wells be plugged to protect safety andenvironmental interests, for example, to protect aquifers and the abovesurface environment.

Wells are most commonly plugged with Portland cement, although a numberof alternative materials have been proposed and are less commonlyutilized. Generally, a well is plugged by pouring Portland cement intothe wellbore, and curing the cement in situ.

It will be appreciated that it would be most uneconomic to attempt tocompletely fill the well bore with cement. Therefore, it has becomewidely known to inject cement into the well in such a way that only thepotential producing zones are blocked off. These potential producingzones were abandoned due to the fact that they were not commerciallyviable; however, for ecological and liability reasons, it is necessarythat these zones be plugged to stop seepage, contamination, andcommunication between zones. The potential producing zones may produceoil, natural gas, various forms of other hydrocarbons, salt water andnatural water. It will be appreciated that in any one well bore, thepotential producing zones may be widely spaced apart; some may beproducing a small amount of oil, others natural gas, while others areproducing water, etc.

Ordinary drilling mud fills the well bore in the regions between thecement plugs. For the cement plugs to be effective, they must beproperly located at the producing zones and must extend a certainminimum distance, say 50 feet, above and below the producing zonethereby to reduce the possibility of seepage.

Formulation of Portland cement in the field is largely a product oftrial and error by field personnel to meet irregularities in thecementing composition and the downhole environment. Cement qualitycontrol is difficult to achieve under such conditions. As a result,Portland cement cured in situ can exhibit cracking, shrinking, or pooradhesion to wellbore tubulars. An imperfect Portland cement plug canenable undesirable fluid flow through the wellbore via leaks along orthrough the cement.

It will be appreciated that the well bore is filled from top to bottomwith a fluid material commonly termed “drilling mud”. Thus, the regionsbetween the various plugs in the well bore will be filled with drillingmud.

On such method for plugging an abandoned well is taught in U.S. Pat. No.4,043,394, and while dated, is fairly descriptive of current methods,and is as follows.

1. Government approval to plug the abandoned well is obtained includingthe specified intervals to plug off the potential producing zones.

2. The drill pipe is lowered downwardly into the well until its lowerend is somewhat below the bottom of where the first cement plug is to belocated. (The position of the lowermost producing zone is known frominformation derived from the well logging operation).

3. The cement volume is calculated having regard to the interval orlength of the cement plug to be placed across the zone or formation, thewell bore diameter and the drill stem dimensions. The reason why thedrill stem dimensions are of significance is that after the cement hasbeen injected the drill stem or drill pipe must be lifted out of thecement and thus the level of the cement will drop by several feetdepending on the displacement of the drill stem including the length ofdrill stem which is lifted out of the cement. Thus, this factor must betaken into account to ensure that the producing zone is properlyplugged. In addition, an extra quantity of cement, nominally 20% abovethat calculated as described above, is included to provide a “safetyfactor”.

4. Cement is then pumped down the drill pipe and exits through its lowerend and then passes up the well bore to a point sufficiently high sothat it will cover the zone required to be plugged as well as providingfor an adequate degree of “safety factor” after the drill pipe has beenlifted above the cement.

5. The drill pipe is then raised upwardly to a point above the top ofthe cement plug. Then, an eight hour waiting period is provided to allowthe cement plug to harden sufficiently as to support at least a portionof the weight of the drill pipe. The drill pipe is then slowly lowereddownwardly until it contacts the hardened cement. This procedure enablesthe plugging crew to determine by “feel” the exact position of the topof the cement plug. The elevation of the top of the plug is recorded andcompared with the base log data to ensure that the cement plug is at theproper elevation. However, if an error has been made in calculating thevolume of cement, or if some of the cement has spread into the producingzone, the plug may be too low, in which event, additional cement willhave to be pumped into the drill hole and a further eight hour waitingperiod provided in order to allow the cement to harden and the locationof the top of the plug located as described above.

6. Assuming the lowermost plug is found to be at the correct depth, thedrill pipe is pulled up to a position adjacent the bottom of where thenext plug is to be located and the procedure described above isrepeated.

A number of patents and patent applications are directed to pluggingabandoned wells, the following of which are only a small few.

U.S. Pat. No. 4,043,394, issued Aug. 23, 1977 to Campbell, disclosesthat in order to plug off potential producing zones in an abandonedwell, cement is injected at the appropriate level in an amount estimatedto be sufficient to seal off the zone. A selected portion of the cement,treated with a radioactive tracer, is injected to provide a layer oftreated cement at the top of the wet cement plug and a probe or loggingtool is thereafter used to locate the position of the top of the plugwith the probe output being recorded graphically to provide a record ofthe position of the plug top.

U.S. Pat. No. 4,730,675, issued Mar. 15, 1988 to Wygant, discloses amethod of plugging an abandoned well with a polymer gel, in which anabandoned well penetrating a subterranean formation is plugged using agel comprising a high molecular weight, water-solublecarboxylate-containing polymer and a chromic carboxylate complexcrosslinking agent.

U.S. Pat. No. 5,343,952, issued Sep. 6, 1994 to Cowan et al., disclosesa method for preventing zonal communication or migration of fluids, in awell to be abandoned, by placement of a cement plug comprising acementitious component, an activator and water.

U.S. Pat. No. 6,098,712, issued Aug. 8, 2000, and U.S. Pat. No.6,750,179, issued Jun. 15, 2004, both to Burts, Jr., both disclose awell plug additive, well plug treatment fluid made therefrom, and methodof plugging a well. The well plug additive includes a dry mixture ofwater soluble crosslinkable polymer, a crosslinking agent, and areinforcing material of fibers and/or comminuted plant materials. Themethod of forming a well plug fluid includes contacting the additivewith water or an aqueous solution, with a method of plugging the wellfurther including the step of injecting the fluid into the wellbore.

U.S. Pat. No. 6,374,915 issued Apr. 23, 2002 to Andrews, disclosesprocesses and apparatus for sealing abandoned well bores which includesincludes a hopper for dispensing comminuted well bore packing materialsuch as a bentonite clay onto an inclined screening surface whichremoves undesired fine materials. A chute for collecting materialflowing off of the screening surface and directing the same into thewell bore is generally funnel shaped. The apparatus includes aneccentric vibrating mechanism for vibrating the inclined screeningsurface to remove the undesired fine materials.

U.S. Pat. No. 6,715,543, issued Apr. 6, 2004 to Svindland, discloses aparticulate matter plug that is placed along all or portions of a wellto be permanently or temporarily abandoned, the plug being arranged tohinder/reduce fluid flow to surface. The plug consists of a mass ofparticulate matter composed of naturally occurring and/or syntheticallyproduced granular matter, including gravel, sand, silt, clay and amixture of these, and preferably of a poorly sorted mass of particulatematter. The granular particulate matter having average particlediameters included in the statistical range of variation of the mass iscomprised of particles with an average particle diameter > 1/256millimeters, thus comprising approximately ⅔ of all particles in themass.

U.S. Patent Application Publication No. 2004/0020651, published Feb. 5,2004, by Burts, III, discloses a well plug additive, well plug treatmentfluid made therefrom, and method of plugging a well. For well plugtreatment to plug an abandoned well, the well plug additive includes adry mixture of water soluble crosslinkable polymer, a crosslinkingagent, and filter aid, and optionally, a reinforcing material preferablyof fibers and/or comminuted plant materials. The method of forming awell plug fluid includes contacting the additive with water or anaqueous solution, with a method of plugging the well further includingthe step of injecting the fluid into the wellbore.

U.S. Pat. No. 6,767,398, issued Jul. 27, 2004 to Trato, disclosescementitious compositions and cementitious slurries for permanentlyplugging abandoned wells and processes and methods therefor. A drycementitious composition which when slurried with water produces aneconomical hydraulic cementitious slurry for closing abandoned wells.The dry cementitious composition is a cement/CKD blend as the majorcomponent with a weight ratio of parts cement to parts of CKD betweenabout 2/3 and about 3/1. Hydraulic cementitious slurries when cured canproduce hard cementitious bodies which will meet or exceed the APIspecification for a competent hard plug. A process for blending thecement and CKD during transit from the cement source to the off-loadsite without requiring further blending after off-loading. Methods areprovided for determining the formulation having the cheapest cost perunit volume of hydraulic cementitious slurry thereby enablingcompetitive quotes based on cf of hydraulic cementitious slurryrequired.

In spite of the advances in the prior art, conventional cement systemssuffer from a 6 hour safety margin to dump the slurry; long set times;low shear bond values; long cement lengths, and long wait on cement(WOC) times causing high expense.

Thus, there still exists a need in the art for improved methods,apparatus and products for abandoning wells.

There also exists a need in the art for improved methods, apparatus andproducts for plugging abandoned wells.

SUMMARY OF THE INVENTION

According to one embodiment of the present invention, there is providedan abandoned well comprising a well bore, and a cementing plugcomprising a polymeric composition, preferably an epoxy composition.

According to even another embodiment of the present invention, there isprovided a method of treating an abandoned well. The method includesproviding a two component polymeric cementing system, preferably anepoxy system, surface mixing the two component system, and then placingthe mixed system in the well.

According to still another embodiment of the present invention, there isprovided a method of plugging an abandoned well. The method includesproviding a two component polymeric cementing system, preferably anepoxy system, surface mixing the two component system, and then placingthe mixed system in the well, and finally allowing the formation of acementing plug to plug the well.

DETAILED DESCRIPTION OF THE INVENTION

The method of the present invention for plugging an abandoned wellinvolves the use of a two part plugging composition, which isincorporated into known plugging methods.

In particular, the two part plugging composition of the presentinvention comprises a two polymeric cementing system comprising apolymeric component and an activator component. The polymeric componentwill in the presence of an activator component be set up, reacted,hardened, cured, catalyzed or crosslinked into a cementing plug.

The polymeric component utilized in the present invention may be anymaterial suitable polymeric material for forming a cementing plug thatwill adequately plug that abandoned well. Examples of suitable polymericsystems include that described in the references cited herein, allreferences of which are herein incorporated by reference. This polymericcomponent may comprise a thermoplastic or thermoset, that is watersoluble or insoluable Preferably, this polymeric component is an epoxyresin.

In the present invention, the polymeric system not only contains thepolymeric material and activator, but may optionally include additivesto improve thermal stability, control set time, generate expansion, andcontrol fluid loss. The additives may be incorporated into the systemdirectly, or into one or both of the components.

Any suitable polymeric system may be utilized, with epoxy systems beingpreferred. In selecting a suitable polymeric system, it is desired thatthe system exhibit one or more, preferably several if not all, of thefollowing characteristics: liquid system that is solid free, noshrinkage upon set up, maintains (or causes an increase in) the wellholepressure; hydrophobic; density allows it to fall thru the well fluid ata suitable rate; and non-gas generating (so as not to cause microchannels).

As utilized in the present invention, the activator component serves notonly to activate, set up, crosslink and/or cure the polymeric compound,but also to accelerate such, so as to reduce the wait on cement (WOC)time. The activator causes the sealant to set under downhole temperatureand pressure conditions at an accelerated rate. Of course, thisactivator component will have to be carefully selected depending uponthe material utilized as the first component.

In the present invention, accelerated set times are generally less than12 hours, preferably less than 10 hours, more preferably less than 8hours, even more preferably less than 6 hours, still more preferablyless than 4 hours, and yet more preferably less than 2 hours.

The activator will cause the polymeric sealant to set under downholeconditions to cause the sealant to bond to the casing and or otherformation surfaces in the well. The pipe may have coating of oil orwater based drilling mud.

The activator component may be selected to not only accelerate cementset, but may optionally be selected to also alter slurry density, cleandownhole surfaces, and/or improve bond.

The activator will be selected for its known property for acceleratingthe setup, activation, cure, crosslinking, of the polymeric material.For the preferred epoxy resin system, activators for epoxies are wellknown, and any suitable one may be utilized. In many instances pairedresin-activator systems are commercially available.

Examples of commercially available materials follows and possibleformulations follow. All materials are Benchmark. All are manufacturedby Resolution Chemicals. Concentrations are parts by weight.

Materials: Epon 862 or 863-resin, Epicure 3046 low-temp hardener,Epicure W high temp hardener, Heloxy 7-primary reactive diluent, CarDuraE10P-secondary, high-temp diluent. Formulations: (1) 100 Epon 862 or863+17 to 40 Epicure 3046 good 50 F to 100 F; (2) 100 Epon 862 or 863+20to 50 parts Heloxy 7+20 to 40 parts Epicure 3046 good 70 F to 125 F; (3)100 Epon 862 or 863+20 to 50 parts Heloxy 7+10 to 20 parts Epicure3046+10 to 20 parts Epicure W good 125 to 175 F; (4) 100 parts Epon 862or 863+0 to 50 parts Heloxy 7+17 to 35 parts Epicure W good from 175 to250 F; (5) 100 parts Epon 862 o4 863+30 to 50 parts Heloxy 7+15 to 25parts Epicure W+0 to 20 parts CarDura E10P good from 250 t0 350 F.

The present invention also contemplates the use of two or more activatorsystems, generally selected to operate at various temperatures to assistin controlling any set, activation, curing, or crosslinking. A blend ofpolymeric material may also be utilized.

The method of the present invention for plugging abandoned wells,includes any of the known plugging methods in which is utilized the twocomponent plugging composition as the cementing material. While ageneralized plugging method is described below, it should be understoodthat any suitable plugging method as is known in the art, including anydescribed above in the backgound or described in any cited reference(all of which are herein incorporated by reference), may be utilizedwith the plugging composition of the present invention.

Very commonly, the plug and abandonment method of the present inventionwill be carried out using one or more of the following steps. A bridgeplug or cement plug is first run into the wellbore and set therein,typically by mechanical means whereby some sealing element extendsradially outward to seal the annular area formed between the outside ofthe device and the casing wall. Thereafter, a perforating gun is loweredinto the wellbore to a predetermined depth and discharged to perforatethe casing. The perforating gun is typically discharged by a firinghead. The firing head used may be pressure actuated firing heads ormechanically actuated firing heads. After the perforations are made, theperforating gun may be retrieved. Thereafter, a cement retainer islowered into the wellbore and set above the bridge plug. The cementretainer, like the bridge plug, acts as a packer to seal an annulusbetween the body of the cement retainer and the casing and isolate thearea where the casing will be perforated. The components of thecementing composition of the present invention are then supplied intothe cement retainer through a run-in string of tubulars attachedthereto. Utilizing pressure, cement fills the isolated area of thewellbore and also extends through the perforations into the surroundingareas in the formation. After the cementing composition is squeezed, therun-in string is disengaged from the cement retainer. Cement is thentypically deposited on the cement retainer as a final plug.

Generally in the practice of the method of the present invention, theresin component and the activator component is mixed at the surface andthen placed downhole at the desired location of the plug and allowed toform into a plug.

Preferably, in the practice of the present invention, epoxy system is eheavier than the well fluid to allow gravity flow thru the well fluid tothe plug location.

Any suitable apparatus and method for the delivery of the components maybe utilized. As non-limiting examples, suitable delivery systems mayutilize a dump bailer, coiled tubing and jointed tubing. They require abase to stack up against such as a packer, petal basket or sand plug.While any suitable delivery mechanism can be utilized, more specificnon-limiting examples of suitable delivery mechanisms include: dumpbailer run on electric line or slick line; pumping through tubing,drillpipe, work strings or any tubulars; allowing fall through fluidsvia gravity; and pumping into an annullas or pipe without displacing(i.e., “bull heading”).

In some instances epoxy system will not have suitable density,specifically, the density may not be greater than that of the wellfluid.

The present invention provides for the utilization of weighting agentadditives to the first component or the second component, or to theresultant combined system, to change the density of the mixed system.Suitable additives to change the density include metal salts, preferablycalcium chloride. Other examples of weighting agents include sand,barite, hemitite, calcium carbonate, FeO, MgO, and manganese ore.Sufficient amounts of the additive are utilized to achieve the desireddensity.

In the plugging method of the present invention the first and secondcomponents are surface mixed. The mixed components are then introducedinto the well fluid at a position on top of sand/petal basket to allowfor in-situ formation of the cementing plug to plug the well.

It should be appreciated that at some point, the density differentialbetween the polymeric system and the well fluid is so low as to resultin too slow of displacement.

On the other hand, it should further be appreciated that at some point,the density differential between the system and the well fluid is sogreat as to result in problems.

Thus, the density differential should be selected so as to providesuitable gravity feed of the system thru the well fluid to the desiredlocation.

Typical densities for the well fluid will be in the range of about 8.33ppg up to about 20.0 ppg, with typical densities for the activator inthe range of about 8.33 ppg up to about 21.0 ppg, and with typicaldensities for the sealant system in the range of about 8.54 up to about22.0 ppg.

It should be understood that other well fluid additives as are wellknown in the art may be incorporated into the first and/or secondcomponent, or added before, along with, or after the introduction of thefirst and/or second component, non-limiting examples of which includesurfactants, surface bond enhancers (non-limiting examples includestyrene butadiene latex, polyvinal alcohols, resins, other adhesives),emulsifiers, ph control agents, fluid loss additives, gas preventionadditive, dispersants, expanding agents, and wetting agents.

Although the present invention has been illustrated by preferredreference to epoxy systems, it should be understood that any pluggingcomposition having two or more components can be utilized in the presentinvention.

All materials cited herein, including but not limited to any citedpatents, publications, articles, books, journals, brochures, are hereinincorporated by reference.

While the illustrative embodiments of the invention have been describedwith particularity, it will be understood that various othermodifications will be apparent to and can be readily made by thoseskilled in the art without departing from the spirit and scope of theinvention. Accordingly, it is not intended that the scope of the claimsappended hereto be limited to the examples and descriptions set forthherein but rather that the claims be construed as encompassing all thefeatures of patentable novelty which reside in the present invention,including all features which would be treated as equivalents thereof bythose skilled in the art to which this invention pertains.

1. A method of treating an abandoned well having a well fluid residingin the well, the method comprising: (A) providing a epoxy resincomponent and an activator component; (B) surface mixing the componentsto form an epoxy system, wherein the system has a density greater thanthe density of the well fluid; and (C) placing the system in theabandoned well.
 2. The method of claim 1, wherein steps (C) and (D) arecarried out utilizing one or more of a dump bailer; pumping throughtubing, drillpipe, work strings or tubulars; gravity flow; and bullheading.
 3. The method of claim 1, wherein the well fluid density is inthe range of about 8.33 ppg up to about 20.0 ppg, the activator densityis in the range of about 8.33 ppg up to about 21.0 ppg, and the resindensity is in the range of about 8.54 up to about 22.0 ppg.
 4. A methodof plugging an abandoned well having a well fluid residing therein, themethod comprising: (A) providing a epoxy resin component and anactivator component; (B) surface mixing the components to form an epoxysystem, wherein the system has a density greater than the density of thewell fluid; (C) placing the system in the abandoned well; and (D)allowing the mixture to form a cementing plug.
 5. The method of claim 4,wherein steps (C) and (D) are carried out utilizing one or more of adump bailer; pumping through tubing, drillpipe, work strings ortubulars; gravity flow; and bull heading.
 6. The method of claim 4,wherein the well fluid density is in the range of about 8.33 ppg up toabout 20.0 ppg, the activator density is in the range of about 8.33 ppgup to about 21.0 ppg, and the resin density is in the range of about8.54 up to about 22.0 ppg.
 7. An abandoned well comprising: a well bore;and an epoxy mixture residing in the well bore.